/**
* Go through all sheets in a spreadsheet, identify and remove all spreadsheet
* import functions, then replace them a while later. This causes a "refresh"
* of the "import" functions. For periodic refresh of these formulas, set this
* function up as a time-based trigger.
*
* Caution: Formula changes made to the spreadsheet by other scripts or users
* during the refresh period COULD BE OVERWRITTEN.
*
* From: https://stackoverflow.com/a/33875957/1677912
*/
function RefreshImports() {
var lock = LockService.getScriptLock();
if (!lock.tryLock(5000)) return; // Wait up to 5s for previous refresh to end.
// At this point, we are holding the lock.

var id = "YOUR-SHEET-ID";
var ss = SpreadsheetApp.openById(id);
var sheets = ss.getSheets();

for (var sheetNum=0; sheetNum<sheets.length; sheetNum++) {
var sheet = sheets[sheetNum];
var dataRange = sheet.getDataRange();
var formulas = dataRange.getFormulas();
var tempFormulas = [];
for (var row=0; row<formulas.length; row++) {
for (col=0; col<formulas[0].length; col++) {
// Blank all formulas containing any "import" function
// See https://regex101.com/r/bE7fJ6/2
var re = /.*[^a-z0-9]import(?:xml|data|feed|html|range)\(.*/gi;
if (formulas[row][col].search(re) !== -1 ) {
tempFormulas.push({row:row+1,
col:col+1,
formula:formulas[row][col]});
sheet.getRange(row+1, col+1).setFormula("");
}
}
}

// After a pause, replace the import functions
Utilities.sleep(5000);
for (var i=0; i<tempFormulas.length; i++) {
var cell = tempFormulas[i];
sheet.getRange( cell.row, cell.col ).setFormula(cell.formula)
}

// Done refresh; release the lock.
lock.releaseLock();
}
}