Japt v2, 21 20 bytes

Saved 1 byte thanks to @Shaggy

e/\[([^[]*?)](./@YpZ

Test it online!

e is recursive replace, which makes one replacement at a time until there are no more matches. In this case, matches of the regex /\[([^[]*?)](\d)/g are replaced with with <inner text> repeated <digit> times until there are no more matches.

According to what I have planned (here), this regex should eventually be at least 3 bytes shorter:

‹[“⁽[»₋”]“.›

Japt v2, 21 20 19 bytes

Saved 2 bytes thanks to @Shaggy

e/.([^[]*?)](./@YpZ

Test it online!

e is recursive replace, which makes one replacement at a time until there are no more matches. In this case, matches of the regex /\[([^[]*?)](\d)/g are replaced with with <inner text> repeated <digit> times until there are no more matches.

According to what I have planned (here), this regex should eventually be at least 3 2 bytes shorter:

‹[“⁽[»₋”]“.›

Japt v2, 22 bytes

e/\[([^[]*?)](\d/@YpZ

Test it online!

e is recursive replace, which makes one replacement at a time until there are no more matches. In this case, matches of the regex /\[([^[]*?)](\d)/g are replaced with with <inner text> repeated <digit> times until there are no more matches.

According to what I have planned (here), this regex should eventually be at least 3 bytes shorter:

‹[“⁽[»₋”]“\d›

Japt v2, 21 20 bytes

Saved 1 byte thanks to @Shaggy

e/\[([^[]*?)](./@YpZ

Test it online!

e is recursive replace, which makes one replacement at a time until there are no more matches. In this case, matches of the regex /\[([^[]*?)](\d)/g are replaced with with <inner text> repeated <digit> times until there are no more matches.

According to what I have planned (here), this regex should eventually be at least 3 bytes shorter:

‹[“⁽[»₋”]“.›

Japt v2, 22 bytes

e/\[([^[]*?)](\d/@YpZ

Test it online!

e is recursive replace, which makes one replacement at a time until there are no more matches. In this case, matches of the regex /\[([^[]*?)](\d)/g are replaced with with <inner text> repeated <digit> times until there are no more matches.

Japt v2, 22 bytes

e/\[([^[]*?)](\d/@YpZ

Test it online!

e is recursive replace, which makes one replacement at a time until there are no more matches. In this case, matches of the regex /\[([^[]*?)](\d)/g are replaced with with <inner text> repeated <digit> times until there are no more matches.

According to what I have planned (here), this regex should eventually be at least 3 bytes shorter:

‹[“⁽[»₋”]“\d›