Step size when Auto numbering

Is it possible to specify step size when auto numbering tracks?
For instance now it numbers tracks 1-2-3-4-5-6
I want to specify step size of 10 and number tracks as 10-20-30-40-50 etc.

You can't with the numbering assistant.
But you can in an action of the type "Format value" for the field:
Format string: $num($mul(%_counter%,10),2)

Thank you! Worked like a charm.

Still, maybe a feature suggestion, add another field in Auto Numbering wizard - "Step size"?

I couldn't found relevant topic..
I'm resorting my whole music library using beets and musicbrainz picard. It's massive so it's taking forever. I spent like 4 hours just on artists that began with the letter A. After getting things right with beets, i realized that roughly half of my albums have the date parameter fomatted as (YYYY-MM-DD) and the other half as (YYYY). So I'm going through my music in musicbrainz picard and manually editing each album to format them as (YYYY).

Is there a way I could edit them all quicker? Like delete anything over 4 characters in the Date id3 parameter for a folder?

There are many ways in MP3Tag to achieve your goal, with actions or the converter.

Example for Converter:
Tag - Tag
Field: YEAR
Formnatstring: $num(%year%,4)
Formatstring: $left(%year%,4)

If you mark all your files that you want to change MP3Tag will do it with one click.