I have a few songs that look like this "4&20" and some like this "4 & 20" How to set the first to look like the second example without disturbing the correct one?
You could try to replace your & character with
space & space
One easy way could be:
Replace the wrongly builded
space space & space space
back to
space & space
I think there could be a regular expression solution for this case.
Maybe I can provide such a solution tomorrow.
are you saying actually type the word space?
No, use a normal space.
It's just nearly impossible to show a space in this forum (using text only):
lol right? But yes I have tried that in actions/replace where it searched for space&space and changed to &, but it affected even the correct ones. The start was "4&20" and changed those to "4 & 20", but the existing ones were changed to "4 & 20"
Try:
Format string: $regexp($replace(%title%,&, & ),\s+, )
Yep, that's what I meant with "change the double space back to space & space" 
@ohrenkino's solution does it in one step 
you guys are awesome thanks!
A note to future readers:
Please be aware that the change from
&
to
⎵&⎵
also changes ARTIST names to a maybe not wanted (not expected) new name.
⎵ is only the visible representation of a space
Bands/Artists with a & in theyr name like
&*!!%
or the japanese singer with the name
&
or the group
Y&T
would be changed to a wrong written new name.
The same is true for ALBUM names. There are dozens of albums with the name
&
and some like
+&+ or -&-
which would be wrongly changed to
⎵&⎵
and
+ & + or - & -
in my collection I have replaced all the "featurings" and "vs" with <& ...>.
So, adding blanks to the & would lead to < & ...> which I would not welcome.
This means that a good knowledge of the data is mandatory to avoid nasty side effects that cause just as much work as getting the other stuff right.