It’s worth noting that the way metadata presets work is the way almost all presets work in Lightroom Classic. The excellent answer by johnrellis is a technique you can use with many types of presets across Lightroom Classic.
For example, if you are working with a metadata preset, file renaming preset, import preset, brush mask preset, etc., in any of those cases you can base a new preset on an existing one because they all have the Save Current Settings As New Preset command. So first make a preset that’s your baseline (containing the settings you always want in new presets), and when you want to make a new preset, start by editing your baseline preset to create a new preset variation, and then choose Save Current Settings as New Preset.