Solution
We create a table variable and populate it with data extracted from a table on a website, using the ConnectHTML command in combination with JavaScript.

Example
The Website contains a list of countries, with population and further data:

We display it in the following form:

GuiXT Script

// Clear the screen
del (0,0) (20,200)

// Display a WebView containing the table from which we extract data
WebView	(8.1,19.3)	(29.2,77.4)	"https://www.geonames.org/statistics/" _
  name="GeoView" -closeonhide

// CreateTable creates a table variable with our needed columns
CreateTable V[GeoTable] rank names country countrycode area _
  namesperkm2 population namesperonethousand

// CopyText reads our javascript code and converts it
// into text and stores it into the text variable code
CopyText fromFile="read_table.js" toText="code"

// Now we execute the javascript code on the webview named "GeoView"
ConnectHTML run="code" runResult="result" name="GeoView"

// Now we copy the results into our table variable
CopyText fromText="result" toTable="V[GeoTable]"

// To show our results on screen we create a table with the needed
// columns by naming the table the same as our table variable
// we retrieve the data from the variable
Table	(8,95)	(29,184)	title="My table" _
  name="GeoTable" rows="&V[GeoTable.rowcount]"
Column "Rank" size=16 name="rank"	
Column "Names" size=16 name="names"
Column "Country" size=16 name="country"
Column "Countrycode" size=16 name="countrycode"
Column "Area" size=16 name="area"
Column "Names per km²" size=16 name="namesperkm2"
Column "Population" size=16 name="population"
Column "Names per 1000" size=16 name="namesperonethousand"

JavaScript - read_table.js

// Retrieve the table element from the sample website
const table = document.getElementById("statistictable");

// Retrieve the table body
const body = table.tBodies[0];   // first (and usually only) tbody element

// Prepare an array to collect the extracted data for GuiXT
const table_data = [];

for (const row of body.rows) {
    for (const cell of row.cells) {
        table_data.push(cell.innerText); 
    }
}

// Return the result as string
table_data.join("\r\n");

Components
InputAssistant + Controls