This is exactly what my RAV4 was doing. Slow leak, wet floor. Interior smelled of coolant. It was a heater leak (18 years old 220K at that time). A new heater core was only about $68 - but I'd have to take the entire dash out (including airbags) just to get at the darn thing. Or spend $800 and have it done - thank you no.
So I figured what the heck, I'll try stop stop leak. After about 200 miles the leak did stop. for about 18 months. It was past winter so I just undid the hose couplings at the firewall, put a pipe between them with clamps and went on my merry way by-passing the heater. Of course no heater or great defroster. The defroster works somewhat because it cuts the A/C in to dry the air. A/C on RAV4 works fine. It got me through last winter. Is the the best way to do it? No. But I didn't want to disassemble car or pay $700. Don't put more than one of these in the vehicle or you'll seal the radiator.
Now I have the former "Allenmobile", henceforth the "Mancermobile." The heater in it works great, A/C doesn't condenser has leak (it was free and didn't have to be towed home) - I'm set for next winter. Being a convertible hot days aren't so bad.
Hope your heater core is easier to get to. It's the proper fix.
In the winter, the Cabriolet and it's heater. On hot muggy days that it won't rain, the the RAV4 with A/C. Not an ideal solution, but it is working me at least.