Trivial Currently, it is not possible to create a new ruler in sequence view with totally custom start position.
However, there is an use-case where this is needed: copy part of some sequence, put it into new doc, add to original sequence view, and add a ruler, where start position is a position of this part in original sequence.
Original seq:
1 2 3 4 5 6 7 8 9
A C T G A G A T G
New seq:
1 2 3 4 5 6 7 8 9
4 5 6 7 8 9 ...
G A G
(copied GAG symbols)