settings-step-input.css

.settings-step-input-container {
    position: relative
}

.settings-step-input-element::-webkit-inner-spin-button, 
.settings-step-input-element::-webkit-outer-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.settings-step-input-buttons-container {
    display: none;
    flex-direction: column;
    position: absolute;
    right: 0px;
    top: 50%;
    transform: translate(0px, -50%);
    height: calc(100% - 4px);
    width: 14px;
    padding: 2px;
    background: var(--theia-input-background);
}

.settings-step-input-container:hover > .settings-step-input-buttons-container {
    display: flex;
}

.settings-step-input-up-button {
    transform: rotate(-180deg);
}

.settings-step-input-button {
    border: none;
    border-radius: 0;
    height: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    user-select: none;
    cursor: pointer;
    line-height: 12px;
}

.settings-step-input-button:hover {
    background: rgba(128, 128, 128, 0.8);
}