Footer custom height

you realy mean the #footer ? or do you like to have a higher socket: #socket ?

well if there is a link to your site in private content area – i do not see as a participant.
If you look to the demo: https://kriesi.at/themes/enfold-2017/#footer
the height is in dependency to the content.
You only have the chance to minimise some paddings or margins – f.e.:
the footer container itself got padding:

#footer {
  padding: 15px 0 30px 0;    /*** top and bottom paddings ***/
}

each widget got a top/bottom margin of 30px

#footer .widget {
  margin: 30px 0 30px 0;    /*** top and bottom margins ***/
}

the widget titles got a top margin of 0.85em

.flex_column .widget .widgettitle, 
.content .widget .widgettitle {
  margin-top: 0.85em;   /*** top margin ***/
}

you can override all these rules with lower values in your quick css