Can I move unused apps to another drive on my Mac?

If they're part of the OS, no. Otherwise, drag-copy them to a volume formatted as any variant of Mac OS Extended or APFS and then delete them from the internal drive.

This won't move preference or other files they've created.

(260555)

These days some apps won't run unless they are in the Applications folder. Other apps may run from another location, but may not update properly or have some other odd behavior. Personally I would not relocate any applications since they generally do not take up that much storage space. It is the user data associated with those applications which generally use up most of the storage.

I would take @den.thed's advice for moving the large data items instead.

For starters take a long hard look at the following support article.

Free up storage space on Mac - Apple Support

If you are looking to free up a considerable amount of internal storage space..?

You can move one or all of your Photos, Music, Movie Libraries to an external hard drive.

Move your Photos library to save space on your Mac - Apple Support

Change where your music files are stored on Mac - Apple Support

Move your iMovie for Mac library - Apple Support

If you move anything to an external hard drive to free up internal storage space.

Then make sure that external drive is also backed up by your Time Machine backup drive.

Back up your Mac with Time Machine - Apple Support

Add on

Applicationa from the Apple Apps Store that are 1 GB and larger can be directly downloaded and installed to "An Other Location " meaning and possibly to an External Drive

Part 1 of 3

System Data technically, has a mount point /System/Volume/Data 

With a mount point of /System , this Volume is part of the Operating System and can not be deleted - full stop

It is where your User Account  was made when the computer was First Setup as New

We can point-out what may be included in this Volume

Though, how to reduce this is a long and complicated trial and error process

This process does not always prove fruitful 

Follow the advise from @den.thed if doing this route

Part 2 of 3

The more  popular way to address this issue is to Start Over from Scratch 

For Apple Silicon computer >> Use Disk Utility to erase a Mac with Apple silicon.

For Apple Intel computers >>   Use Disk Utility to erase an Intel-based Mac followed by How to reinstall macOS

Always make a Time Machine Backup  before  proceeding 

It is also suggest to  Only Migrating the User Account and nothing more.

Emphasis on User Account Only

Reinstall the Needed and not the Wanted applications from the Apple Apps Store or Directly from the Developers 

Part 3 of 3

Generally when this type of issue is discovered by the User ( you in this case )

It is because the Internal Drive Capacity of this computer maybe on the small size

Meaning, the computer has a 256 GB Capacity Drive or possible the 512 GB Drive Capacity 

Unfortunately, the users' needs for Storage may have grown since the time it was originally purchased 

The implications being that, on your next purchase

Spend the Extra Money Up Front on a larger Drive Capacity Drive and add more RAM

This may just Future Proof the computer for your growing needs 

Just saying,  we get what we have paid for 

You can't move any of the Apps installed by macOS if that's what you are asking.