the 10 speed links, were they powerlinks/similar? In which case how did you get them to link up? 10 speed powerlink’s pins being shorter than 6/7/8speed, and so you can’t get them through the inner plates of the chain and locked properly.
Otherwise, iirc the space between the inner plates on a 10 speed chain is also narrower so if you used a few bits of 10speed to lengthen the chain, you might find that the 10speed bit jumps on the smaller sprockets under heavy load as it doesn’t sit all the way into the teeth as well.
Finally i don’t have great experience of rejoining ‘geared’ chains for derailleur systems (ie ones that aren’t bmx chains with massive outer plates and wide pins) without using proper joining pins or quicklinks/powerlinks; they tend to fail after a while at the point you pushed the pin back into the outer plate. Fine to get you home if you break a chain, but will break again later on at most inconvenient moment.