Features used to implement the example

• Boolean validator with math, date-time or text-string terms
• Validatior based on regular expression

Example: Make a custom field mandatory when priority is "Critical" or "Blocker" and issue type is "Incident"

We will be able to implement this requirement using Boolean validator with math, date-time or text-string terms. I have implemented it successfully in a beta version of the plugin using the following configuration:

Or to implement it we can use validator Validaton based on regular expression with the configuration shown in the following screenshot:

Note that:

• To evaluate the value of fields Priority (field code %{00017}) and Consequence of bug (field code %{10700}) at the same time we compose a text with both fields using character '@'  as separator.
• We check  "Negate validation" since the regular expression introduced describes the kind of input we don't to admit.