Extract the name of a point with Regular Expression

ClearAll[f]
f = StringCases[RegularExpression["(^.+)="] :> "$1"] 

f /@ {"A1=(345.2345,3423.1)",  "B=(2123,97.123)", "KX=(2144.546,-4455)"}

{{"A1"}, {"B"}, {"KX"}}

Use positive lookahead:

ClearAll[f]
f = StringCases[RegularExpression["^[^=]+(?==)"]];

f /@ {"A1=(345.2345,3423.1)", "B=(2123,97.123)", "KX=(2144.546,-4455)"}

{{"A1"}, {"B"}, {"KX"}}

Another way, without using regular expressions

StringSplit[#, "="] & /* First /@ {"A1=(345.2345,3423.1)", "B=(2123,97.123)", "KX=(2144.546,-4455)"}

{* {"A1", "B", "KX"} *)

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