You can't.  Add a new segment, then use Item Number change.

Hi,

I can't create a new segment it'll exceed my total char length and I can only create one more segment.

You can't change the total length, so you're stuck.

Is it possible to decrease the value of the 'Code' segment and increase the 'Brand' segment?

Only with careful and detailed data surgery of at least 40 tables.   

But by the way, you can have more than 20 in the total of all segments, just not together in one item structure:

I can't create more than 4 segments. the program gives an error.

Too bad, that means you're on a cheap version of Sage.  You'll have to upgrade, or contact a data repair company.

Oh ok...

thanks for the support.

Could you create the new segment 4- make it a long segment.

Change all your items to this segment code.

then you might be able to change the length of the segments in options, at worst via SQL. then do another Item change.

So do a two part item change to get to your desired result?

Of course you should create a test database and do all this in that company first.

You must use SQL to do this, I've done it before.  If there are only a few items and a few transactions in the database, a non-professional with SQL experience could do it.  But if OE and PO are involved, you have to be super careful to keep ICITEM.FMTITEMNO equal to POPORL.ITEMNO, PORPCL.ITEMNO, OEORDD.ITEM, etc. on any open transactions. PO is especially breakable.