Adjustable Capacitance Circuit
The way it is drawn, as mentioned by @jaysotola, you have a short between A and B.  That last node should be removed, regardless of context.
If you are looking at n- or p- Farad values, they do make variable capacitors.  Some can be large, like some of the old school radio tuners,  or small, like a little trim-pot, but it's a capacitor instead.  There may be higher values available, but I'm not sure on that.
Practicality would probably be pathetic, but perhaps you could make your own.  Take two straps of foil, make them really smooth, put some sort of dielectric between them (not sure on the specifics here. Experiment time!), and Bam!  Capcitor.  Press them together with something flat and insulating, and you change the capacitance.  A search on YouTube for &quot;DIY capacitor&quot; will lead you to some more info on caps like this.