You do that easily using TV Recording Rules, rather than Tag Rules.
The image attached shows a complex recording rule I use for Doctor Who. Don't worry about trying to understand the first five lines, because they are very specific to my EPG data and are a logic nightmare!
Take note of the last three lines of rules. They are all enclosed in the one set of brackets () which means that they have an OR statement between them.
The first line says record anything from Season 00, which is the Specials. I always record the Specials as I never know when they will be aired.
The next line record anything from Season 1, because I was missing a couple of Episodes and wanted to fill the gap in my collection.
The third line says record anything in Season 10 or later seasons.
In the Rules box on the left you can see the "English" version of those three lines. ([Season]=[00] or [Season]=[1] or [Season]=>=10)
The rule you should add is much simpler. Just add a Rule that says "Season is 4", and MC should format that to mean all your existing rules AND the new rule that the Episode must be from Season 4 must be true. The AND statement is always assumed in these rules unless an OR is specifically included by wrapping the rules in brackets (). The new rule should just add;
[Season]=[4]
