Usually, yes—lighting umbrellas are fairly robust, roughly comparable to a normal rain umbrella. They can often travel fine in a regular backpack or simple long bag if you protect them from bending, crushing, and heavy abrasion.

Dedicated cases are often just basic long canvas bags, not necessarily highly protective hard cases, so a specialty bag is not always essential. In practice, many photographers carry umbrellas, stands, and small modifiers in ordinary bags such as gym bags.

For other light modifiers, it depends on the type. There is too much variety to generalize, but many are mostly fabric and also travel well if packed carefully. Bulk can be a bigger issue than durability, especially in a camera backpack that is already full.

So the key factors are:

• avoid crushing or bending
• separate sharp/heavy items from fabric modifiers
• make sure the bag is long enough for stands/umbrellas
• accept that any field gear can be damaged over time

If the modifier is lightweight and your packing prevents mechanical stress, a regular bag is often good enough.