With the FWL16 keyboard being QMK there is another option, that while far from ideal, might be good enough until someone does a proper trackpad with buttons.
QMK can do mouse clicks. And with some use of QMK tapdance, combos, and / or macros you could do whatever you want, click-drag, clicking left & right mouse together.
If clicking both buttons is one thing that really needs to be solved, you could say, program tapdances with the Right-Alt, and Right-Ctrl keys. Quickly tap and immediately hold Right-Alt for Left Mouse button. And the same for Right-Ctrl for Right Mouse button. Do them together, Right & Left Mouse button together.
Now Via (the point-and-click configuration interface for the keyboards located at keyboard.frame.work) doesn’t offer the ability to configure QMK tapdance or combos. But a community member created a Vial/QMK port. Keyboard: VIA / VIAL support? - #50 by Allen_S. Vial is an alternate point-and-click configuration interface that does offer tapdance & combos, as well as other features Via lacks. https://get.vial.today. Currently, Vial/QMK firmware is available for ANSI keyboards and the macropad.