HTC is reportedly teasing multiple interaction capabilities for the U12 Plus via a tweet that it recently sent out on its account earlier this morning. Though not too enlightening when it comes to any and all interactions, HTC does hint at a few things. First, in the tweet context itself HTC says "Touch. Tap. Control. More." which seems to be suggesting that users will be able to have more control over the device interaction functions through touching and tapping, though this could really just be referencing interaction with the touch display, which would be nothing new.
Based on the graphic in the tweet's GIF though, it seems clear that HTC is teasing the squeeze action that was debuted with the HTC U11 called Edge Sense. In the GIF, what looks like a phone-shaped device can be seen under a sheet that looks as if it's being squeezed just where you would be holding and squeezing the phone's sensors. That said it probably isn't too shocking that HTC would introduce its next flagship smartphone with this capability considering its last flagship smartphone had it as well, and this is in addition to the HTC-made Google Pixel 2 series devices which came after the HTC U11 that also offered more or less the same exact functionality.
The only other detail from HTC is the date of its upcoming event which is listed as May 23, 2018, a date which is already known since HTC officially announced the date of its event back on May 3. Though HTC isn't giving out any specific details the teaser is pretty clearly referencing Edge Sense, and the "more" in the tweet could be referring to Edge Sense getting more functionality than what has already been on offer. If that ends up being the case then HTC would essentially be beefing up the original interaction with more stuff that it could do to make using the phone more convenient.