Vivaldi multiline tabs and wide pinned tabs.css

#tabs-container {
  height: auto !important;
}
.resize {
  display: block !important;
}
.tab-strip {
  display: block;
}
.tab-strip > span {
  display: inline-block;
}
.tab-strip > span > .tab-position {
  left: 0px !important;
  position: relative;
  height: auto !important;
  width: auto !important;
}
.tab-strip > span > .tab-position > .tab:not(.pinned){
  width: 120px !important;
}


.tab-strip > span > .tab-position > .tab.pinned{
  width: 120px !important;
}

.tab-strip > span > .tab-position > .tab.pinned > .tab-header > span.title:before {
  content: '*';
  font-family: "Courier New", serif;
  margin-bottom: -20px;
}


.tab-strip > .newtab {
  left: 0px !important;
  top: 0px !important;
  position: relative !important;
  display: inline-block;
  padding: 0;
  vertical-align: top;
}
.tab-header > .favicon > svg {
  height: 17px;
}

#tabs-container .tab.tab-small.tab-mini .tab-header .title, #tabs-container .tab.pinned.tab-mini .tab-header .title {
 display: flex !important;
}

Just append contents of this gist to the end of the common.css file:

On Windows common.css is located at %localappdata%\Vivaldi\Application\VIVALDI_VERSION\resources\vivaldi\style
(replace VIVALDI_VERSION with the currently installed Vivaldi version, for example - 2.2.1388.37).