I'm putting in quite a bit of work making terrain pieces for my styles resizable, but it does occur to me that other people using these styles may not use this feature to its fullest, just because there's no indication of which pieces are resizable. It should be relatively simple to add this: arrow icons in the top-right of each piece's window, <-> for horizontal and the flip of that for vertical.
I second this suggestion definite +1 from me
if this applies for terrain, it should apply for objects as well.
Not a bad idea - I also see no reason why this should be limited to terrain pieces only. ;)
Implemented in SLX Editor commit bc360ce.