Can Bilstein inserts in a Boge strut be removed without taking off the strut?
 

Title is my question. Can the Bilstein insert in a Boge strut be taken out and replaced without removal of the entire strut assembly?

And likewise without alignment?

Yes and no.

insert can be R&R but alignment should be reset.

I have details of this in my build thread, but in a nutshell:

Remove the tie rod nut and drop the tie rod off the spindle.
Take the sway bar loose from the chassis - this allows you to drop the strut enough to angle it beyond the fender (narrow body)
Remove the safety washer and nut from the strut
Connect an old coat hanger to the hub and the body so that you don't rest the strut assembly on the brake line when the strut is disconnected
The strut can be angled beyond the wheel well and the strut removed.

I have a video near the end of my thread where I tightened up the gland nut as well. Might be useful.

You shouldn't have to do another alignment. Only if the tie rod length is disturbed or the camber /toe bolts at the top of the strut housing disturbed would an alignment be necessary. Your test drive after will tell as well.