This is one of the bad things about smart bulbs. There is no physical way to control them. Long term, my advice is to invest in smart switches, you can get a Zooz switch or dimmer for about $25-$30 and are much easier to automate with.
Do you have any smart switches in maybe the kitchen or an adjacent room you could use in Motion Lighting "Switch to Disable Turning Off" option?
If you are sitting still that long at dinner, all the food would be gone at my house. 
Why not just extend the timeout and/or move the sensor a bit if it can't see you. At least as a temporary fix.
Now there are times where I do think you need an override switch of some type. A button would be ideal. Ask if you want recommendations about one.
For Alexa I would try the following.
- Create a virtual switch, maybe called "dinner time". Add that to the Alexa skill.
- In Motion Lighting, use this as your "Switch to Disable Turning Off" option in Options for Additional Sensors, Lights-Off and Off options.
- The following app could turn this virtual switch off after a period of time, and possibly the bulbs too? I have never used this particular app, but it looks like it would work.
You can install Hubitat Package Manager or manually install the app above. I would encourage you to try the Package Manager though, it really streamlines things. This is in the Convenience section of that app.
