You could use for example following in the *.uew file used to syntax highlight the language:
This block contains two case-insensitive Perl regular expression search strings.

The first one is for finding procedures.

^ ... start each search at begin of a line.

[\t ]* ... find a horizontal tab or space zero or more times. So a procedure line can have leading tabs/spaces.

proc ... after optional leading tabs/spaces the line must have the keyword Proc.

[\t ]+ ... find a horizontal tab or space one or more times.

(...) ... capturing/tagging group. The string found by the expression inside the group should be displayed in the hierarchical function list.

[a-z_] ... find case-insensitive a single letter in range A-Z or an underscore.

[0-9a-z_]* ... find case-insensitive any digit or letter in range A-Z or underscore zero or more times.

The inner group defines first a block start and a block end condition with \( and \). The block to search with the second regular expression should start after first occurrence of an opening ( found from beginning of a found procedure line and end before first occurrence of a closing ) found after opening ). This means for the example procedure line that the block to search with second regular expression is:

TaskID As Word, TaskAddr As Dword, Priority As Word, Start As Word

The meaning of second Perl regular expression is:

\s* ... find any whitespace character according to Unicode standard including newline characters zero or more times. So the parameters of a procedure can span also over multiple lines.

(...) ... once again a capturing group for getting just the string matched by the expression inside this group displayed in hierarchical function list.

[a-z_] ... find case-insensitive a single letter in range A-Z or an underscore.

[0-9a-z_]* ... find case-insensitive any digit or letter in range A-Z or underscore zero or more times.

[\t ]+ ... find a horizontal tab or space one or more times.

As ... the next word must be as in any case.

[a-z]+ ... find case-insensitive any letter in range A-Z one or more times to match the type of the variable.

,? ... find a comma zero or one times, i.e. optionally matching a single comma.

I posted /Regexp Type = Perl and you inserted into your wordfile /Regexp Type = perl. The keywords in syntax highlighting wordfiles are case-sensitive. So UltraEdit does not recognize perl and the regular expressions are interpreted with UltraEdit instead of Perl regular expression engine.

I suggest to use following in your wordfile:
Note: The character between " and % in second line must be a tab character and not a space character.

The regular expression search string " ^ symbol" does not make much sense to me. ^ is interpreted as begin of a line. So it is not possible that a space character is left to it.

I suggest to use:

^[\t ]*Dim[\t ]+([a-z_][0-9a-z_]*)[\t ]+as[\t ]+(?:bit|byte|word|dword|float|sbyte|sword|sdword)\>

(?:...) ... non capturing group with an OR expression of several words. One of the words in the OR expression inside non-capturing group must be found. Question mark and colon after opening parenthesis makes this group a non-capturing group.

[ ... ] ... is a character class definition, i.e. a list of characters from which one of the characters in this list must be found.

\> ... end of word to ignore variable names like ByteCount. \b ... word boundary could be also used.

For aliases: ^[\t ]*Dim[\t ]+([a-z_][0-9a-z_]*)[\t ]+as[\t ]+(?!(?:bit|byte|word|dword|float|sbyte|sword|sdword)\>)

(?!...) ... negative lookahead.

Please note that a lookahead or lookbehind must be of fixed length, i.e. the search function must know how many characters to look ahead or behind. For that reason + or * can't be used in a lookahead/lookbehind expression. But an OR expression with each argument of fixed length is possible because the Perl regular expression engine can determine how many characters to look ahead or behind by determining the longest OR argument.