The closest thing I can think of to a single-click method for applying multiple keywords to a photo is to create a metadata preset:

• In the Metadata panel, pull down the Preset drop-down and say Edit Presets...

• Click "Check None" to clear any existing preset

• Scroll almost all the way to the bottom of the list to the Keywords section. Type your keywords into this box, just as you would into the Keywording panel.

  As soon as you start typing here, you will notice that the checkbox next to "Keywords" gets checked. This is telling you that this setting (and this setting alone) will be applied when you use this preset.

• Pull down the drop-down at the top of the window and say "Save Current Settings as New Preset..." This will let you name the preset for later use.

• Click Done to leave this dialog. Now you will find that the Metadata → Preset drop-down has your new preset in it. When you select it, those keywords will be added to those already on the photo.

This is clearly only suitable if you have a static set of keywords you can define up front. You can use multiple presets on a single photo; the effects merge, rather than replace the prior values.

When you can't really define the necessary sets up front, you pretty much have to give up on your "without typing" restriction. Once you do set that restriction aside, several more solutions become available:

1. Type your long set of keywords into the Keywording box once, say ⌘/Ctrl-A to select your typing, hit ⌘/Ctrl-C to copy the text to the clipboard, then hit Enter to apply those new keywords to the selected photo(s). Now you can find the next photo or group of photos that needs that same keyword set and ⌘/Ctrl-V them onto that set, too.

   I do this all the time, and it really is not that big a deal. The most painful part about it comes from the fact that Lightroom really starts choking when you get into heavy keywording, but that is going to affect any solution as long as keyword application in Lightroom remains slow.

   (Adobe, if you're listening, that's my top LR6 wishlist item: instantaneous keyword application. A net data addition measured in the 10's of kilobytes should not be taking human-scale time in 2015.)

2. cmason's Keyword Shortcuts answer.

   It's essentially the same thing as the previous option, but you don't have to keep your input focus in the Keywording text box, and Shift-K is easier to hit than ⌘/Ctrl-V Enter.

3. Use the Paint tool to do the same thing with the mouse instead of the keyboard:

   • In the Grid view, click the spraypaint can icon in the toolbar.

     (Press T to show it if it isn't showing already.)

   • From the drop-down box next to the "Paint:" label, select Keywords.

   • Type your long list of keywords in, separated by commas:

     

   • Spraypaint those keywords onto the photos in the grid.

Whichever option you choose, I suggest that you combine it with some kind of Text filter. If you're adding the example keyword set above, you can say ⌘/Ctrl-F, then set a filter to make Lightroom hide the photos you've already changed:

The key trick is the ! prefix on the keyword combined with the "Contains Words" option. This tells Lightroom to show you all the photos that do not contain that keyword. Thus, as you add keywords to photos, they disappear from the filtered grid, allowing you to see other photos that you might also want to change.

This is different from using "Doesn't Contain" in two key ways:

• You can use it in combination with positive terms. For example, you could find photos that are almost certainly missing at least one keyword with "models !style !gender".

• "Doesn't Contain" uses substring matching, so that it can't make a distinction between "top" and "octopus". As your keyword hierarchy gets deeper and broader, you will cause more and more of these collisions. Whole-word searching will reduce their impact.

With sufficient cleverness, you can often get the Library Filter to do things you might have thought you'd need a Smart Collection to accomplish.

By the way, your use of commas in keywords (e.g. "Chabalier, Pierrette") causes problems with all of the solutions above. "Lastname, Firstname" is fine for paper filing systems, but it offers no benefits in Lightroom. I suggest that you switch to one of two alternative schemes:

• If you have some OCD organizational need to have the Keyword List panel arranged by last name, use Lightroom's keyword hierarchy feature: "Chabalier > Pierrette".

• Spell the name out naturally: "Pierrette Chabalier". Lightroom treats that as two words, so you can still search for just "Chebalier", if you want to.