You can use below content for you customer_account.xml to add new link there in My Account sidebar section
<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" layout="2columns-left" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd" label="Customer My Account (All Pages)" design_abstraction="custom">
<body>
<referenceBlock name="customer_account_navigation">
<block class="Magento\Framework\View\Element\Html\Link\Current" name="custom-link-left-sidebar">
<arguments>
<argument name="label" xsi:type="string" translate="true">Custom Link Left Sidebar</argument>
<argument name="path" xsi:type="string">custom/index/index</argument>
</arguments>
</block>
</referenceBlock>
</body>
</page>
In above content you can use your Block class name instead of using Magento\Framework\View\Element\Html\Link\Current this
You can remove any link using below line in your xml file
<referenceBlock name="your-block-name" remove="true" />
You can add your block name where I have mentioned 'your-block-name'. For e.g. If you want to remove wishlist link then you can find block name of wishlist link here in this file..
vendor/magento/module-wishlist/view/frontend/layout/customer_account.xml
there is one block with this name "customer-account-navigation-wish-list-link" that is your wishlist link block you can use this name in referenceBlock name and just add remove="true" after it.
After adding this you can clear and flush cache using commands
php bin/magento cache:clean
php bin/magento cache:flush
Hope this may help you!