I have a little sheet…in which I enter data…I quite like sheets…it goes with my use Devonthink for everything policy…

However in DTTG I can’t enter data in the fields?

Correct. Sheets cannot be edited in DTTG2 at this time.

Is editing sheets in DTTG on the roadmap?

It is definitely on our (considerable) list of all things DTTG2.

Is there a timeline for this?

Sheets can be created and modified if you have made the in-app purchase of the Pro Pack (see DEVONthink To Go’s Settings > Manage).