mahta- (1) vb. "wield a weapon", "fight" (MAK), "to handle, wield, manage" (VT39:11, VT47:18), also "deal with" (VT47:6, 19, VT49:10). Past tense mahtanë is attested (VT49:10). In an earlier version of the entry MAK in the Etymologies, Tolkien first glossed mahta- as "slay [or kill] with sword", then changed it to "fight with sword" (VT45:30-32)
Quenya
mahta-
verb. to handle, wield, use, make use of; to manage, deal with, treat, control, to handle, wield, use, make use of; to manage, deal with, treat, control; [ᴹQ.] to stroke, feel; to wield a weapon, fight
mahta-
wield a weapon
mahta-
trade
[mahta-] (2) vb. "trade", changed by Tolkien to manca-, q.v. (VT45:33)
mahta-
verb. handle
handle, deal with, manage, wield, treat
manca-
trade
manca- ("k")vb. "trade" (MBAKH, VT45:33)
A well-attested verb whose original sense seems to be “handle”, based on the root √MAH or √MAƷ for “hand”. It had other glosses such as “wield, use, make use of”, but also “manage, deal with, treat, control”. It thus seems to be usable for both “handle, wield, use” a concrete physical item and “handle, manage, deal with” an abstract process or situation.
Conceptual Development: In The Etymologies of the 1930s the verb ᴹQ. mahta- meant “stroke, feel, handle; wield” as a derivative of ᴹ√MAƷ “hand” (Ety/MAƷ), but also “wield a weapon, fight” as a derivative of ᴹ√MAK “sword; fight (with a sword)” (Ety/MAK). Earlier versions of the entry for ᴹ√MAK had glosses like “slay with sword” or “kill with sword” (EtyAC/MAK), which seem to be holdovers from ᴱQ. makta- “slay, slaughter” from the Qenya Lexicon of the 1910s under the early root ᴱ√MAKA (QL/58).
Neo-Quenya: For purposes of Neo-Quenya, I would use mahta- for both “handle” and “fight” (mainly in the sense “wield a weapon”) as a blending of √MAH and √MAK, along with the meaning “stroke, feel” a physical thing.