In Acid Machine, I have created a kind of virtual 4 channel mixer, that is the only thing that connects directly to the main destination output. All osc nodes that are generated by an instrument get connected to the instruments master gain node, then that connects to one of the mixer channels. All mixer channels then connect to a master mixer gain, then the output.
If you do it that way, you just need to attach the recorder to the master output of the mixer.
it's also decent practice to send your oscillators into a mixer anyway so that they can be rerouted at large.
for instance, say you have 4 oscillators, 2 fx buses and an output. you route (4 oscillators) -> mixer -> fx bus 1 -> output. then if you want to switch the fx bus for your oscillators, you can just reroute the mixer instead of each oscillator individually.
in the case of a recorder, you'd want the end of your entire graph to look like this: mixer -> recorder -> output. this way your recorder is capturing all audio (oscillators, effects, etc). (and, as noted above, you have the option to reroute the mixer directly to the output when it's not recording).
My mixer channels are a gain node (for input), followed by 2 gain nodes - which are used as fx slots and replaced when an effect is added, the last fx slot connects to another gain node (for channel output) - that then connects to the mixer master gain node.
You could have it as simple as 1 gain node for each channel which you use for input and output to the mixer master gain. This would make it difficult to add fx later though.
if all you're trying to do is combine nodes in the graph a gain node is standard. (that is, you can connect any number of oscillators to a single gain).
If you do it that way, you just need to attach the recorder to the master output of the mixer.