On Version 1.3.15 / Untuntu 20.04:
When I select multiple rems and then try to use the alt + arrow to move them up or down, I can only move them down. In other words, alt + up arrow moves the down and alt + down arrow moves them down.
Also, when I select multiple rems and try to re-parent using ctrl + shift + m, they disappear from view. If I use the “three dots” menu to the left of the rem and try to re-parent, I can only re-parent one at at a time, even if multiple are selected (though I think this is just how that works for the time being, not a bug). However, I can re-parent using ctrl + shit + m just fine when I’ve only got a single rem selected (via the active cursor being on a given rem).
I suppose these could be separate bugs but considering that the functionality works fine otherwise, that these two behaviors only come up when multiple rems are selected, I am grouping them together