Discussed possible solutions:
1. skipTags in project settings. setting will be applied for all test suites and test cases. possible problems: platform dependant tests.
2. dynamic test suites: Add "Exclusion Tag List" to test suite, make appropriate UI changes (excluded test will be marked). In this case we will get dynamic test suite with exclusion list.
Cons: one test case can belong to many test suites, in which it can be included exluded at the same time.
3. do not save eclusion list for project. Put exclusion list under Q7 preference page. In this case exclusion list will be applied for all projects.