If we store a bike trailer in a large bag, we can handle it easily while it is detached from the bike.
I use a bike trailer to attach folding bike Brompton and I store them in my room. My room is at upper floor of an apartment and I can’t take an elevator with them attached.
I started storing my bike trailer in a bag. A tote bag made by DAISON DE UN MAILLOT (width 72cm, height 53cm, depth 28cm, capacity 100L) fits my trailer, MULTI-USE CYCLE TRAILER DCP434-DP made by DOPPELGANGER.