riot-web/res/css/views/settings/tabs/_PreferencesSettingsTab.scss

/*
Copyright 2019 New Vector Ltd

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

.mx_PreferencesSettingsTab .mx_Field {
    margin-right: 100px; // Align with the rest of the controls
}

.mx_PreferencesSettingsTab .mx_Field input {
    display: block;

    // Subtract 10px padding on left and right
    // This is to keep the input aligned with the rest of the tab's controls.
    width: calc(100% - 20px);
}