[circonian]

Actually I figured it out...partially:

if not MyAbilityTooltip then
    --AbilityTooltipTopLevel
    --ZO_Tooltip
        MyAbilityTooltip = CreateControlFromVirtual("someUniqueName", ZO_Compass, "ZO_Tooltip")
        local ZO_Dyeing_Gamepad_Tooltip_Styles = ZO_ShallowTableCopy(ZO_TOOLTIP_STYLES)
        ZO_Tooltip:Initialize(MyAbilityTooltip, ZO_Dyeing_Gamepad_Tooltip_Styles, style)
    end
    
    MyAbilityTooltip:ClearAnchors()
    MyAbilityTooltip:SetOwner(self, TOPLEFT, 100, 100, TOPLEFT)
    
    InitializeTooltip(MyAbilityTooltip, GuiRoot, TOPLEFT, 100, 100, TOPLEFT)
    
        local upgradeSection = MyAbilityTooltip:AcquireSection(MyAbilityTooltip:GetStyle("abilityUpgradeSection"))
        MyAbilityTooltip:AddSectionEvenIfEmpty(upgradeSection)
    MyAbilityTooltip:LayoutAbility(abilityId, hideRank, overrideRank, pendingChampionPoints, addNewEffects)

But it takes up the whole screen and MyAbilityTooltip:SetDimensions(xx, yy) seems to have no effect. The styles are messing it up, going to try to write my own style table for it, to change dimensions & see if that works.