In an overlay plot you can simply "Normalize X" on the scaling tab under plot options. This might work well for UPLC vs HPLC comparisons.
Alternatively, if you needed a little more control over the scaling you could use Derived Channels in the Method Set. Under the Filter/Offset Channel, you can define parameters for "RT Offset / Scaling". This allows you to take the original channel and define start/stop time and convert them to a derived channel start/stop time.
ASR&D - Process Definition Analytical
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