[N1 (Mirko)]

Same excercise for Mercury. The next conjunctions to watch (besides proper Transits, which are more frequent than Venus ones) are:

5 November 2026 at 22.4' separation
13 May 2029 at 23.2'
4 May 2036 at 25.7'
and
7 November 2039 at 13.9'

(assuming a solar radius being about 16' so the closer to that the better)

That last one should be pretty cool as it's an actual Transit happening really close to the limb. Shallow angles like that benefit most from H alpha observing, as they can be extended more than steep angle events, relatively speaking.

Edit: Hα observation with very large prominences that happen to be in the right place at the right time (extremely unlilkely), will really be the only way to see any of these conjunctions except for the 2039 event as Mercury has no brilliant atmosphere that could make it visible this close to the Sun. I'm guessing Mercury has to be several degrees out from the Sun to be visible at all.