Thanks for reaching out. That is a great question. Let me see if I can clarify that for you.
Could you please confirm the version of Lightroom that you are using? Is it Lightroom Classic or Adobe Lightroom, along with the operating system you are using? Adobe Lightroom current does not have local adjustment presets as such.
If you are on Lightroom Classic, the Radial/Linear Gradient & the Brush tool are part of masking, also categorized as Local Adjustment tools. Which supports presets of the values available as sliders.
Select either the Brush tool or the Radial/Linear gradient
Go to Effects > Custom > Dropdown menu > Select any presets or 'Save Current settings as New Preset' to create your local adjustment presets.
Please note: Adjustment Brush tool presets do not include brush-specific options like Size, Flow & Density.
We hope this helps. Please let us know if it does.