The bowL does not have enough water. can we at least increase the waterlevel in the bowl?

The water level in the bowl is in part controlled by the casting of the china itself, and the flow of water from the refill tube. If there was room in the toilet tank for a taller flush valve, you might be able to slightly increase the tank's volume by adding something to increase the height of the flush valve. I don't know if it is even possible on those units as I haven't serviced one. The fill valve would have to be adjusted as well. A 1" fernco, or a flexible trap adapter coupling may help out your situation until the toilet could be replaced with a higher quality unit, such as a Toto Drake.

Good points, KC. My first thoughts were: is the current fill valve adjusted so the tank fills up to the water line, and; could the be a issue with the vent situation on the drain side that somehow is siphoning the bowl down?

Not likely with the vent. Previous thread stated 1.28 gpf.

Unless the bowl is NOT Filling up to its design water level, there is nothing you can do to raise it. IF it can use more water then you have a problem with the small refill tube going into the overflow pipe.

ditto hj

you can NOT raise the bowl fill level above the weir of the bowl's integral trap

any additional water merely drains away

the small refill tube's purpose is to fill the bowl - if restricted, no proper fill

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

You are assuming that the weir of the trap is at or almost at the maximum level of the the design, and that this isn't simply a 1.6 gallon per flush toilet with a short flush valve.