How can I modify the filter for the gadget "Watched issues"?

[Dylan]

How i can limit the issues and have in this filter only these ones updated the last 2 weeks for example?

[Joe Pitt]

I wouldn't mess with the built in filters. You can create your own search and share it.

[Nic Brough -Adaptavist-]

You can't change it without hacking the code behind it.  Don't do that, use a filter and a fitler-resutls gadget as Joe says.