Unfortunately online support for flask is somewhat limited. It is not treated as a mature web programming language. But I use it mainly for internal demo purpose, and it simplifies things tremendously. The trick is often that a technique is not specific to flask, but html in general.
It is relatively easy to redirect to a new tab with a hyperlink in html:
<a href=”google.com” target=”_blank”> my awesome link </a>
will do that.
With forms, target is a top level attribute that controls rendering of the entire form
<form target=”_blank”> … <input type=”submit” value=”submit”> … </form>
To redirect to new tab for an individual button within the form, try
<form> … <input type=”submit” value=”submit” formtarget=”_blank” > … </form>
I also found that POST actions do not support Ctrl + Click, since the target url cannot infer the POST parameters directly.
Several useful links on flask: