slip composing: shift container

As far as I know you can't set containers relative to another unrelated container, in other words its offset is relative to its parent or the global container. Also, don't know if it will work but you should be able to use the synfire timing notation to get finer grained control, 1m = 1bar, 1m+1/2 = 1bar + half bar, 1/3 = triplet, etc. You even be able to use tick notation.

Right, if I understand correctly you want to be able to set the grid in the structure view so you can move containers at a finer grain than 1 measure. If I remember correctly in synfire 1 there was shortened version of the grid snap selection in what is now structure or matrix view: that allowed you to change how finely you could drag a container. Maybe it was in Harmony Navigator? Or if I am remembering incorrectly there was a shortcut near the top left of the keyboard that let you switch between different snapping settings: something like 1,2,3,4 or q,w,e,a,. I can't seem to find it either but haven't needed it bad enough or maybe have adapted and made my music more "blockular" and start and end at bar divisions, haha. I miss it too. Not sure if that's what you're talking about.

Ok I did  a little digging through the Synfire 1 manual and a little experimentation and the grid snap division seems to be tied to the zoom level, but are limited to bar and quarter bars. Intuitive in a way but I'm still haunted by the memories of the old shortcuts to change grid divisions.

Fine resolution depends on zoom. One beat of the time signature is the finest resolution. The mouse is not useful for finer steps. You can type any offset and length in the inspector.