.env-list-panel {
  $width: 315px;
  box-sizing: border-box;
  width: $width;
  margin-left: -20px;

  &:before {
    @include diamond($white);
    top: -8px;
    left: 30px;
    width: 13px;
    height: 13px;
    border-width: 1px 0 0 1px;
    border-style: solid;
    border-color: rgba(0, 0, 0, .1);
  }

  .env-list {
    margin-left: 0;

    &__input {
      box-sizing: border-box;
      padding: 10px 10px 8px;
      margin: 10px 10px 0;
      width: $width - 20px;
    }

    &__environment {
      position: relative;
      // The items need to be above the diamond.
      z-index: 1;
      list-style-type: none;
      padding: 10px 20px;
      margin-bottom: 0;
    }

    &__environment:hover,
    &__environment:focus {
      background-color: $hover-background;
      cursor: pointer;
    }

    &__last-connected {
      color: $warm-grey;
    }

    &__message {
      padding: 10px 10px 0;
    }
  }

  .create-new-model {
    padding: 10px;
  }
}

.env-list-panel {
  $width: 315px;
  box-sizing: border-box;
  width: $width;
  margin-left: -20px;

  &:before {
    @include diamond($white);
    top: -8px;
    left: 30px;
    width: 13px;
    height: 13px;
    border-width: 1px 0 0 1px;
    border-style: solid;
    border-color: rgba(0, 0, 0, .1);
  }

  .env-list {
    max-height: 300px;
    overflow: auto;
    margin-left: 0;

    &__input {
      box-sizing: border-box;
      padding: 10px 10px 8px;
      margin: 10px 10px 0;
      width: $width - 20px;
    }

    &__environment {
      position: relative;
      // The items need to be above the diamond.
      z-index: 1;
      list-style-type: none;
      padding: 10px 20px;
      margin-bottom: 0;
    }

    &__environment:hover,
    &__environment:focus {
      background-color: $hover-background;
      cursor: pointer;
    }

    &__last-connected {
      color: $warm-grey;
    }

    &__message {
      padding: 10px 10px 0;
    }
  }

  .create-new-model {
    padding: 10px;
  }
}

Set a max height for the list of models.
Set a max height for the list of models.
