MS-Access Debug Watch value length is limited

It is best to use the intermediate window for this. I frequently do this with SQL queries for this reason.

To show this, use "View--> Intermediate Window" (or Control+G).

Then use syntax like the following:

debug.print "This is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long stringThis is a really long string"

And you can select and copy/paste out of the intermediate window or scroll to see the whole variable.

Note that the intermediate window does not get cleared automatically but you can select everything and delete it whenever you want.