Hi Andreas, welcome to the forum! I’ve taken the liberty to move your post into a new thread, because the other was getting a bit crowded with a mix of different topics.
There is no public roadmap available, though obviously we’ve got plans for the near future, and our internal roadmap and wishlist for the longer term. We don’t discuss those in detail publically, but we’re always interested to hear about what users need for their individual workflow.
Custom tuning for fretted instruments is certainly something we aim to have available in the Score Editor, but I can’t make specific promises as to when that will happen.
You can move notes to a different string with the Cross Staff entries in the Score menu (5 line stave and tab stave must be visible for that currently), or with the key commands “Move To String”, which don’t have a default shortcut set.
We are still considering the best way to make guitar techniques such as hammer-ons, pull offs, tapping available in the Score Editor. In Dorico, you would find the via the ornaments popover or the Guitar Techniques section in the properties panel.