Weapon Planar Level Experience
 

There is currently no way to see how much "experience" your Planar Weapon has except immediately after adding a Planar Weapon Essence essence, when the amount of experience currently and needed for the next level is displayed in your chat window.

Somewhere in the weapon's examine window, you should be able to see "X experience of Y total experience needed for next planar level".

I believe I saw someone mention that this information is visible via Census.

Is this feasible?

Census is a whole different animal than the UI unfortunately. The examine window is probably the most heavily hard-coded window in the game in terms of how it all populates.

I did a quick look through the gamedata file just in case and don't see any dynamic data for it either unfortunately (it'd have to be on the examine window, since its part of the item's data rather than character data. Unfortunately it'd be up to Daybreak to add it to the window - on the upside, the amount per planar level has thusfar been consistent, you just can't know if you're partway through without going to the zone and adding one. I just save them up until I have enough for the next level and do them in one big go.

Hmm. Would it be possible to stick a button on the examine window that said "Get Planar Experience" that would make a Census call to grab the info?

That way you wouldn't have to do that unless someone called for it, and the button wouldn't need to be visible on anything except planar weapons/secondaries that were not fully leveled.