I am pasting a sample may this give you any idea.
---Input box filters the Table rows
---RESET clear the filter
TEST.qvw 141.8 K
I came up with a solution to reset the variables. You can use an Action "Set Variable" and give a NULL to the value. So you basically reset your variable (you can put a text or button "clear...."). This also solves the other problem because by assigning NULL you practically cancel any constraint.
But I would still like to know how you "hold on" and apply multiple filters one upon the other. For instance first set a min weight, get 70/100 results and then set a max and get 50/100 etc. Now I get the same results but in both cases I use > and <, but NULL cancels one of them until it gets a value.